CODEWITHSUNDEEP
javascriptnode.js
Sang
Sang

Reputation: 4454

How to compare 2 pairs of numbers?

How to efficiently compare 2 pairs of numbers?

Is [a, b] > [c, d] equivalent to a > c || a === c && b > d in Javascript?

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Edit question: how does Javascript evaluate [a, b] > [c, d] expression?

Upvotes: 0

Views: 1021

Answers (4)

Redu
Redu

Reputation: 26191

You are trying to do a nested comparison such as on strings. You may simply do like;

[1,3].join() > [1,2].join() // <- true

or ugly but by coercing

[1,3]+"" > [1,2] // <- true

Upvotes: 0

doubleOrt
doubleOrt

Reputation: 2507


For your problem, you should use the solution you added in your question: a > c || a === c && b > d, and it is not inefficient at all.

If you are repeating the same task multiple times, then go create a function for it: 

function custom_comparison(a, b, c, d) {
return a > c || a === c && b > d;
}


Edit: the first part of my answer was clearly wrong, @rockStar's answer is the correct one in that regard, so I just deleted my explanation.

Upvotes: 0

user8897421
user8897421

Reputation:

"Is [a, b] > [c, d] equivalent to a > c || a === c && b > d in Javascript?"

No, the correct results you're getting is because of the single digit numbers you're using. See below.

"how does Javascript evaluate [a, b] > [c, d] expression?"

Because you're not comparing numbers, they two arrays get converted to strings. So substituting the numeric values for the variables, we may get this:

"1,2" > "0,3"

This does work as long as you always have single digit numbers.

Try this: 

[10, 2] > [2, 1]

Suddenly it fails. This is because the lexical comparison of "10,2" and "2,1" places the second value at a greater position.

Upvotes: 2

Nina Scholz
Nina Scholz

Reputation: 386766

You could take a function for an arbitrary length.

function isGreater(aa, b) {
    return aa.some((_, i, a) =>  a[i - 1] === b[i - 1] && a[i] > b[i]);
}

console.log(isGreater([1, 2], [3, 5]));
console.log(isGreater([3, 2], [3, 5]));
console.log(isGreater([3, 6], [3, 5]));
console.log(isGreater([4, 2], [3, 5]));

Upvotes: 0

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